Load levelling and anti-sway trailer hitch

ABSTRACT

A trailer hitch is provided with a ball and socket coupling and load levelling bars which are arranged for a pivotal movement about an axis coincident with the axis of the ball and socket coupling. The arrangement for pivoting the load levelling bars includes a two-part articulated housing member for receiving the ends of the load levelling bars which is provided with an antifriction plate arranged for cooperation with a complementary braking surface. The housing member is coupled for rotation with a first beveled cam disc which cooperates with a second beveled cam disc, both of which are concentric with the axis of the socket to provide a variable load levelling force to each bar upon rotation of the housing about the axis. A hitch receiving socket is secured to a draw bar and either the socket or the entire draw bar assembly is pivotably mounted under the control of an adjustable resilient device to control the load levelling forces applied to the load levelling bars.

United States Patent [1 1 Thompson [451 Apr. 2, 1974 LOAD LEVELLING ANDANTI-SWAY TRAILER HITCH [76] Inventor: Woodrow F. Thompson, Highway 80,West Forest, Miss. 39192 [22] Filed: May 19, 1972 [21] Appl. No 255,238

Primary Examiner-Leo Friaglia Assistant ExaminerRandall A. SchrecengostAttorney, Agent, or Firm--Sughrue, Rothwell, Mion, Zinn & Macpeak [5 7]ABSTRACT A trailer hitch is provided with a ball and socket coupling andload levelling bars which are arranged for a pivotal movement about anaxis coincident with the axis of the ball and socket coupling. Thearrangement for pivoting the load levelling bars includes a two-partarticulated housing member for receiving the ends of the load levellingbars which is provided with an antifriction plate arranged forcooperation with a complementary braking surface. The housing member iscoupled for rotation with a first beveled cam disc which cooperates witha second beveled cam disc, both of which are concentric with the axis ofthe socket to provide a variable load levelling force to each bar uponrotation of the housing about the axis. A hitch receiving socket issecured to a draw bar and either the socket or the entire draw barassembly is pivotably mounted under the control of an adjustableresilient device to control the load levelling forces applied to theload levelling bars 6 Claims, 12 Drawing Figures PATENIEUIPR 2m SHEU 10F 4 FIG. I

FIG. 2

PAIENTEDAPR 2 1974 SHEET 2 I]? 4 FIG. 3

PATENTEBAPR 21974 SHEET 3 0F 4 FIG 6 aiem; 13s

PATENTEDAPR 2 I974 SHEEF t UP 4 PW. W

FIB ii LOAD LEVELLING AND ANTI-SWAY TRAILER HITCH BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to a new andimproved trailer hitch and more particularly to a trailer hitch havingimproved load levelling and anti-sway characteristics.

2. Prior Art Although prior art devices have previously incorporatedload levelling mechanisms in combination with a trailer hitch, thesetrailer hitches commonly utilized a pair of angularly related bars whichwere pivotally connected to the towing vehicle at two spaced-apartlocations. Such a construction, although achieving the load levellingfeature for which they were intended, provided a serious draw-back sincethe rods or bars were pulled out of line when turning. Such a push-pullaction tended to cause a severe side pull or swaying action whichseriously affected the operators control of the towing vehicle.

Prior art trailer hitch devices also incorporated antisway devices whichusually consisted of means for retarding the push-pull action of theload levelling bars referred to above. Other prior art devices attemptedto provide a frictional restraint on the pivotal movement of the trailerportion of the coupling about a vertical axis relative to the draw barportion of the coupling. These frictional anti-sway devices however,relied solely upon a pre-set frictional force and did not take intoaccount variations in the load and the degree of turning movement.

The best known prior art arrangement is disclosed in applicants own US.Pat. No. 3,588,145 which is directed to a load levelling and anti-swaycontrol trailer hitch. In this patent, the load levelling bars areconnected at one end to a housing which is mounted for pivotal movementabout a vertical axis on the main coupling body coincident with the axisof the ball and socket connection. Jack means are provided on thetrailer tongue for applying a load levelling force to the load levellingbars and friction plate means are secured to the upper surface of thehousing for frictional engagement with a complementary friction surfaceon the main coupling body. Although the frictional force is directlyrelated to the strain placed upon the load levelling bar, no means areprovided for varying the load levelling forces in the individual barsrelative to the ,degree of pivotal movement of the housing about thepivot axis. Applicants prior patent also discloses means for pivotallymounting a coupling receiving member on the towing vehicle andcontrolling the pivotal movement by resilient spring means. However, nomeans are disclosed for controlling the resilient means to therebycontrol the angular position of the coupling receiving member andthereby control the force applied to the load levelling bars.

SUMMARY OF THE INVENTION The present invention is directed to a trailerhitch having cam means for controlling the load leveling force appliedto each load levelling bar dependent upon the degree of pivotal movementof the load levelling bars about the axis of a ball and socket couplingincident to the relative turning movement between a towing vehicle and atrailer.

The present invention is directed to a trailer hitch having draw barmeans including pivoted coupling receiving means which is pivoted underthe control of resilient means which are adjustable to vary the positionof the pivoted coupling receiving means.

The present invention is directed to a trailer hitch having a ball andsocket coupling and a pair of load levelling bars which are supported atone end of the trailer tongue and at their opposite ends by a two-partarticulated housing which is mounted for pivotal movement about an axiscoincident with the axis of the ball and socket coupling. The two partarticulated housing is coupled to a beveled cam member which isoperatively engageable with a beveled cam disc concentrically disposedrelative to the axis of the ball and socket coupling. Friction platemeans are secured to the housing and are disposed in complimentaryfrictional engagement with a frictional surface on the main body of theball and socket coupling whereby the frictional force between thefriction plate and the friction surface will be directly proportional tothe load levelling forces applied to the load levelling bars. The mainbody of the ball and socket coupling is detachably received in a socketmember which is pivoted under the control of adjustable resilient meansto vary the position thereof and thereby vary the force applied to loadlevelling bars and to dampen vibrations attendant to travel over roughsurfaces.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of a preferred embodiment of the invention as illustrated inthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view,partly in section, of the trailer hitch according to the presentinvention.

FIG. 2 is a top plan view, partly in section, of the hitch shown inFIG. 1. I

FIG. 3 is a top plan view of a draw bar assembly according to thepresent invention.

FIG. 4 is a side elevation view of the draw bar assembly shown in FIG.3.

FIG. 5 is a sectional view of the draw bar assembly along the line 55 inFIG. 3.

FIG. 6 is the top plan view of a modified draw bar assembly.

FIG. 7 is a side elevation view of the modified draw bar in FIG. 6.

FIG. 8 is a top plan view of a modified load leveling bar arrangement.

FIG. 9 is a sectional view taken along the line 9-9 in FIG. 8.

FIG. 10 is a front elevation view, partly in section of a jackarrangement for the load levelling bars on a trailer tongue.

FIG. 11 is a top plan view of the arrangement shown in FIG. 10 with thejack removed.

FIG. 12 is a sectional view along the line l2-l2 in FIG. 11.

DETAILED DESCRIPTION OF THE INVENTION The two principal features of thepresent invention relate to the load levelling and anti-sway arrangementin the trailer hitch per se and the means for accomplishing the loadlevelling in the draw bar assembly. It is contemplated that the twoaspects of the present invention may be utilized together or separatelyin combination with other prior art arrangements. For example, thetrailer hitch arrangement shown in FIGS. 1 and 2 could be utilized withthe draw bar arrangement shown in FIGS. 3-5 or it could be used with anyother draw bar arrangement as long as the draw bar had a socket capableof receiving the attachment member for the trailer hitch. Likewise, thedraw bar assembly shown in FIGS. 3-5 inclusive could be engaged with thetrailer hitch shown in FIGS. 1 and 2 or with any other type of trailerhitch which is capable of being mounted in the hitch reqeiving socket onthe draw bar assembly.

Turning first to the trailer hitch arrangement shown in FIGS. 1 and 2,it is noted that the arrangement shown therein is very similar to thearrangement shown in FIGS. 28 and 29 of applicant's prior U.S. Pat. No.3,588,145. The principal differences reside in the load levelling andanti-sway frictional arrangement.

The main body portion of the trailer hitch is provided with a forwardlyextending connecting bar 12 which is adapted to be received in anysuitable socket on a draw bar arrangement. Any suitable means may beutilized for retaining the bar 12 within such a socket. A depending ballmember 14, is shown disposed in a complementary socket 16 in the mainbody portion 10 of the trailer hitch assembly. The socket 16 is enlargedto form an additional chamber 18 at one side thereof for the receptionof a locking bar 20. The locking bar is normally spring biased upwardlyby means of a spring 22 surrounding a bolt 24 which is pivotally securedto the lower end of the locking bar and loosely retained within thepassage 26 extending through the flange 28 of the body portion 10 bymeans of a bolt 30. A pivoted operating lever 32 is connected to theupper end of the bar 20 by means of a connecting link 34. The bar 20 isnormally biased upwardly and outwardly of the chamber 18 in order toallow the ball 14 to be inserted in the socket 16. Once the ball 14 isdisposed within the socket 16, the lever 32 may be pivoted to force thelocking bar 20 downwardly into engagement with the ball 14 to hold thesame within the socket 16.

The ball 14 may be secured in any suitable manner to the forward end ofthe tongue of a trailer. The arrangement shown in FIG. 1 discloses theball 14 as being secured to an adaptor plate 36, which in turn, hasanother ball 38 extending upwardly therefrom for insertion into thestandard downwardly opening socket arrangement 40 which is secured tothe tongue of a trailer. The plate 36 may be bolted to the socketportion 40. A dust cap 42 is biased downwardly to cover the ball 14 bymeans of a spring 44. It is also possible to utilize a reversearrangement wherein the ball member would be secured to the main trailerhitch body 10 for cooperation with the standard downwardly openingsocket member 40 on a standard trailer tongue. Such an arrangement wouldbe similar to that shown in FIG. 40 of applicants prior U.S. Pat. No.3,588,145. A guide plate 46 is secured to the upper surface of the hitchbody 10 to enable the ball member 14 to be guided upwardly into thesocket 16 during a semi-automatic coupling operation. Such asemi-automatic coupling arrangement is described more fully in detail,along with variations thereof, in applicants prior U.S. Pat. No.

The main body portion 10 of the trailer hitch is provided with aforwardly extending recess 48 to provide suitable clearance forthepivotal action of the load levelling bar arrangement to be describedhereinafter. A bolt 50 extends downwardly to an opening in the bottomcenter of the socket l6 and is threaded into the base of the main bodyportion 10. The bolt 50 acts as a pivot pin for the load levelling bararrangement and is coaxially aligned with the axis of the depending ballmember 14 when it is disposed in the socket 16. A first circular beveledcam disc 52 is disposed on the supper surface of the base 54 of the mainbody 10. The cam disc is provided with a depending key member 56 whichcooperates with a complementary groove 58 in the base 54 to prevent therotation of the cam disc 52 relative thereto. A flat thrust washer ofbrass, copper or the like is disposed on the upper surface cam disc 52and a second beveled cam disc 60 which is complementary to the firstbeveled cam disc 52 is disposed on the upper surface of the washer 55 sothat the two cam discs and washer define a right cylinder having an axisconcentric with the axis of the bolt 50 and ball member 14. The uppersurface of the cam disc 52 lies in a plane which is angled upwardly andrearwardly from a low point adjacent the forward end of the hitch body10. Both of the cam discs 52 and 60 are provided with a central aperturethrough which the bolt 50 freely extends. The upper surface of the disc60 is provided with a narrow raised transversely extending horizontalsurface 59. A pair of pins 62 and 64 are provided on the upper surface59 of the cam disc 60 for engagement with complimentary sockets in theload levelling bar assembly.

The load levelling bar assembly is comprised of a pair of housings 66and 68 each of which have a rearwardly opening socket 70 and 72, as bestshown in FIG. 2, for the reception of the forward ends of the loadlevelling bars 74 and 76. The load levelling bars 74 and 76 may be offairly rigid steel stock or of resilient spring steel depending on theforces needed and may have any suitable configuration. The loadlevelling bars extend rearwardly and are supported by suitable means tobe described hereinafter. on the trailer tongue. The forward end of eachof the housings 66 and 68 are provided with sockets 63 and respectively,for reception of the pins 62 and 64 on the upper surface of the cam disc60. A pair of upwardly extending brackets 78 and 80 are secured to theupper surface of each of the bar receiving housings 66 and 68respectively, adjacent the rearwardly extending openings for the socketsand 72. At the upper ends of the brackets 78 and 80, a pair oftransversely extending aligned bores 82 and 84 are formed for thereception of a connecting rod 86. The connecting rod 86 is securedwithin the bores against longitudinal displacement but the brackets 78and are free to pivot about the rod 86.

The main body 10 of the trailer hitch is provided with a rearwardlyextending flange 90 having a flat semicircular under surface 92. Afriction brake plate, having a friction liner secured thereto anddisposed in engagement with the surface 92, is provided with a downardlyextending bracket 96 which is adapted to extend over the rod 86 tosupport the friction plate member 94 in operative frictional engagementwith the surface 92. The exact configuration of the flange 90 and themanner in which the brake member 94 is operatively disposed between theflange and load levelling bar housing is similar to that arrangementshown in FIGS. 30 and 31 of applicants prior U.S. Pat. No. 3,588,145.

Turning now to the operation of the load levelling and anti-swayfeatures of the present invention, it is clear that an upwardly directedforce may be applied to the ends of the load levelling bars 74 and 76 byany suitable means such as the jack member described hereinafter. Thisupward force is transmitted to the main body of the trailer hitchassembly, which in turn, will transmit a force to the draw bararrangement to distribute the load forwardly on the towing vehicle sothat the rear end of the towing vehicle will not be unduly lower thanthe forward end thereof. In the straight line towing condition where thetrailer is in direct alignment with the towing vehicle, the cam discs 52and 60 will be disposed as shown in FIG. 1. In such a condition, theupward force of the load levelling bars 74 and 76 is imparted throughthe brackets 78 and 80 and the friction plate 94 to press the frictionliner 95 into frictional engagement with the lower surface 92 of theflange 90. Such a frictional force tends to minimize any tendency forthe trailer to sway out of alignment with the towing vehicle. However,during a turning operation where a misalighment of the towing vehicleand the trailer is intentionally brought about, the load levelling barswhich are secured to the trailer will cause the load levelling barreceiving housings 66 and 68 to pivot relative to the axis of the bolt50. Due to the fact that the housings 66 and 68 are coupled to the camdisc 60, the cam disc 60 will rotate relative to the cam disc 52, thuscausing the thicker portion of the cam disc 60 to ride up on the thickerportion of the cam disc 52. Such a turning movement will transmit anadditional force through the respective housing 66 or 68, depending uponthe direction of turning and thereby place an additional lifting forceon one of the load levelling bars 74 or 76 through the respectivehousing member 66 or 68. This additional load levelling force will betransmitted forwardly to the towing vehicle in proportion to the angleof turning movement to help compensate for the sway forces imposed onthe turning vehicle during the turning movement. Thus, the loadlevelling force applied to one of the load levelling bars will beincreased and the load levelling force in the other bar decreased duringany turning operation to assist in maintaining control of the towingvehicle and trailer at all times.

For example, look at FIG. 2 and assume a right turn as being made. Therelative movement between the cam discs 60 and 52 will cause the pin 62to rise and the pin 64 to fall. The rising movement of the pin 62 willraise the housing member 66 and apply an additional lifting force to theload levelling bar 74 disposed therein. The housing 68 will be relievedof pressure but the downward movement of the housing 68 will be limitedby engagement of the innermost portion 69 of the housing on the uppersurface of the disc. This slight relative movement between the housings66 and 68 is compensated for by the pivotal movement of their housingsabout rod 86. The increase in pressure on the bar 74 and the decrease inpressure on the bar 76 will impart a turning torque in a clockwisedirection about the connector 12 as viewed from the rear of the car ortowing vehicle. Since the left side of a car tends to dip downwardly ina right hand turn this clockwise torque will be in opposition to the dipor sway of the car and therefore tend to level the car.

Turning now to the draw bar assembly as illustrated in FIGS. 3,4,5, apair of side plates 100 and 102 are provided and may be rigidly securedto the frame of the towing vehicle by any suitable means. Since theattachment means are well known in the art such as bolts or welding, itis not deemed necessary to go into detail with respect to this matter. Apair of cross tubular members 104 and 106 are connected between theplates and 102 and in turn are connected by a plurality of shortconnecting members 108. A socket member 110, extends rearwardly from thetruss member, centrally thereof for receiving the connecting bar of atrailer hitch similar to the bar 12 shown in FIG. 1. As statedpreviously, any suitable means may be provided for retaining the barwithin the socket 110. The socket member 110 is pivoted to the cross bar106 by means of a hinge 112. A control box 114 is secured to the twocross bars 104 and 106 by any suitable means, such as welding or thelike and is provided with an aperture 116 through which the forwardlyextending end of the socket member 110 extends. Within the control box114, a pair of resilient members may be provided on the top and bottomof the socket member 110 to resiliently support the same.

In the simplest form of construction, the resilient members may be inthe form of resilient rubber blocks which will act to dampen thevibrations imparted through the socket member 110 due to rough roadconditions. It is also contemplated that coil spring means or any othersuitable resilient means could be utilized for this purpose.

A more sophisticated arrangement of resilient means may be provided inthe form of air bag similar to the conventional air bag utilized inautomotive spring devices. In this embodiment, the member 118 isillustrated as a simple resilient block and member 12 is illustrated asan air bag having means for varying the pressure therein. The pressurefor the air bag would be supplied from a suitable source on the vehiclesimilar to those air pressure sources now available on certain models asoptional equipment. Suitable controls may be provided on the dashboardof the vehicle, whereby the pressure in the resilient air bag 120 may beselectively controlled, to thereby vary the force by which the socket110 is held against the block 118. Such a variation in the force appliedto the socket 110 will, of course, vary the operating characteristics ofthe load levelling bars assuming a trailer hitch similar to that shownin FIGS. 1 and 2 is utilized in conjunction with the draw bar in FIGS.35. With such a means for controlling the load levelling force, it ispossible to do away with the conventional jack member which is usuallyused to raise and lower the rear ends of the load levelling bars. Byusing the air bag arrangement, the device is capable of absorbing minorfluctuations due to rough road conditions to provide a smooth ride whichwill aid in the control of the vehicle and trailer at all times.

By utilizing the air bag arrangement for controlling the application offorce to the load levelling bars and by using a hitch similar to thatshown in FIG. 1, the operation of connecting a trailer to a towingvehicle is almost entirely automatic. With the trailer tongue disposedat the proper level by means of the trailer support rod, it is possiblefor a single person to merely back up the towing vehicle to the trailer.The use of the guide plate 46 will enable the automatic coupling of theball 14 within the socket l6 and since the plate 46 is fairly wide, thedegree of skill required in backing up the towing vehicle is reduced toa minimum. With the air pressure reduced in the air bag 120, it is aneasy task to insert the load levelling bars 74 and 76 into a suitablebracket on the trailer tongue and into the sockets 70 and 72 on thetrailer hitch. The air will then be supplied automatically to the airbag 120 by means of a suitable control on the dashboard of the vehicleto apply the proper load levelling force through the load levellingbars.

Instead of using the pivoted socket member 110 as shown in theembodiment of FIGS. 3-5 it is also possible to maintain the socketmember rigid with the truss assembly and pivot the entire truss assemblyrelative to the vehicle on which it is mounted. As shown in FIG. 6, thedraw bar is comprised of a pair of cross tubular members 130 and 132connected together at different levels by means of short parallelconnecting members 134. A rearwardly extending connecting member 136 isrigidly connected to the members 130 and 132 and is provided with arearwardly opening socket 138 for the reception of the connecting bar ona trailer hitch. A pair of forwardly extending arms 140 and 142 aresecured to the opposite ends of the cross members 130 and 132. A pair ofbracket members 144 and 146 are rigidly secured to frame members 148 and150 of the vehicle. Each bracket is provided with a socket member 152and 154 respectively. Pin members 156 and 158 are secured to oppositeends of the cross member 132 and are rotatably received within thesocket members 152 and 154 respectively.

Adjacent the forward ends of the arms 140 and 142, a pair of brackets160 and 162 are mounted on the channel shaped frame members 148 and 150of the vehicle. Inflatable air bags 164 and 166 or any other suitabledevice such as piston and cylinder arrangement are disposed within theopen ended chambers formed by the bracket on the vehicle frame memberswith the forwardly extending bars 140 and 142 resting on the uppersurface thereof. Each of the relatively small volume air bags 164 and166 are disposed in constant direct communication with a substantiallylarge volume compensation air bag 168. An air pressure source 170isprovided at any suitable location within the vehicle and is connectedto the compensation air bag 168 through suitable conduits and the flowof air to and from the air bags can be controled by suitable valve means172.

The operation of this embodiment is similar to the operation of theembodiment shown in FIGS. 3-5. Prior to connecting a trailer to thetowing vehicle, the air bags 164, 166 and 168 would be deflated byoperating the valve 172 to the exhaust position. A hitch member,generally shown at 174 in FIG. 8 would then be coupled to the connectormember 136 of the draw bar assembly. The hitch shown in FIG. 8 issimilar to that shown and discussed in detail in FIGS. 1 and 2 but inthis instance, the load levelling bars 176 and 178 would not extendparallel to each other but would diverge rearwardly along the framemembers 180 and 182 of the trailer tongue. Since the load levelling willbe accomplished by the air bags on the draw bar assembly, it isunnecessary to utilize a jack arrangement for lifting the rear ends ofthe load levelling bars. Accordingly, a pair of simple brackets 184 and186 are merely hooked over the frame members 180 and 182 as shown inFIG. 9 and secured thereto by means of set screws 188 and 190. Therearwardly extending end of the load levelling bars 176 and 178 aremerely supported by the brackets 184 and 186 since it is unnecessary toprovide any vertical adjustment to the load levelling bars at thispoint.

When the trailer tongue is coupled to the hitch memher by the ball andsocket connection, the load levelling bars may be easily inserted intothe sockets on the hitch member and into the brackets 184 and 186 on thetrailer tongue. Under these loading conditions, the rear end of thetowing vehicle would be substantially lower than the forward end of thetowing vehicle and in order to level the towing vehicle, air pressure issupplied to the air bags 164, 166 and 168 by turning the valve 172 toprovide communication from the air pressure source 170 to the air bags.As the air bags 164, 166 inflate, the forward ends of the side arms and142 of the truss assembly are raised upwardly as viewed in FIG. 7 andthe loading forces imparted by the trailer to the rear end of the towingvehicle are distributed forwardly of the vehicle to level the same.Thus, it is no longer necessary to use the jack assembly on the trailertongue to apply the load levelling forces to the vehicle and trailer butthe same can be accomplished by the simple turning of a valve which maybe conveniently located on the dashboard of the towing vehicle. Also,with this arrangement it will be no longer necessary to have differentsize and strength load levelling bars. It will only be necessary toregulate the pressure within the air bags and a suitable gauge or lightarrangement may also be provided on the dashboard to indicate the properamount of pressure needed for any particular load. Since it is no longernecessary to have the jack assembly on the trailer tongue, the presentarrangement would be more readily adaptable to trailers having tonguesof different configurations. The system for controlling the inflation ofthe air bags in FIG. 6, may also be utilized to control the inflationand deflation of the single air bag arrangement previously shown in FIG.3.

Even though it will be possible to eliminate the need for a jack on thetrailer tongue while using the air bag arrangement described in theprevious embodiments, there are so many instances where a jack assemblywill be necessary to apply the load levelling forces to the bars wherethe hitch is used with a draw bar arrangement which is not pivoted orprovided with air bags. An improved type of jack assembly for applyingload levelling forces to the load levelling bars is shown in FIGS. l0l2inclusive. Numerous trailers are being built today wherein the tongue isprovided with a center bar 200 as well as the two converging side bars202 and 204. As a result, it is more difficult to adapt a jack to thetrailer tongue so that the forces may be applied to load levelling barswhich extend rearwardly in a position substantially to and beneath thecenter bar 200 of the trailer tongue.

According to the present embodiment a pair of angle irons 206 and 208are mounted transversely of the trailer tongue. It is also possible toutilize square tubular stock or any other suitable stock in lieu of theangle irons. An inverted U-shaped bracket 210 is bolted to and extendsbetween the two upright portions of the angle irons 206 and 208. Thebracket 210 does not extend the entire length of the angle irons 2.06and 208 but only extends on opposite sides of the center bar 200 adistance sufficient to support a jack assembly. A transversely extendinggroove 212 is formed in the middle of the bracket 210 and a pair of jackpost receiving apertures 214 and 216 extend through the bracket 210 onopposite sides of the center bar 200. A joint member 218 is mounted on aplate 220 by an suitable means. The plate 220 is substantiallycoextensive with the support bracket 210 and is formed with a transversegroove 222 which is adapted to rest in the groove 212 in the bracket210. The curvature of the groove 222 is such that when the plate 220 isdisposed horizontally the flanges of the plate are spaced from the uppersurface of the bracket 210. This is best shown in FIG. 12. The jack 218is provided with a post 224 which may be raised and lowered by anysuitable means either mechanical or fluid. The post 224 bears on thecross bar 226 which is secured at its opposite ends to a pair ofvertically extending posts 228 and 230. The posts 228 and 230 extenddownwardly through guide sleeves 232 and 234 which are secured in theapertures 214 and 216 by any suitable means such as welding or the like.The post 228 and 230 are interconnected at their lower ends by means ofa pair of parallel spaced-apart cross bars 236 and 238. Divider pads orblocks 240 and 242 are secured to each of the cross bars 236 and 238 toprevent the load levelling bars which rest thereon from slidingtransversely of the bars. As the result of having two parallelspaced-apart cross bars 236 and 238, it is possible to obtain twodifferent load levelling characteristics for every setting of the jack.In order to hold the jack in any particular setting, each of the posts228 and 230 are provided with a plurality of notches 244 which cooperatewith pivoted pawl members 246 and 248 pivoted to the guide sleeves 234and 232, respectively. Since the jack support plate 220 is substantiallycoextensive with the bracket plate 210, the plate 210 must also beprovided with apertures therethrough sufficiently large to allow thepassage of the guide sleeves 232 and 234 therethrough with sufficientclearance to allow pivotal movement of the plate 220 relative to thebracket 210. The pivotal movement between the plate 220 and the bracket210 is limited by the forward and rearward edges of the plate 220contacting the upper surface of the angle irons 206 and 208respectively. The pivotal movement allows for minor forward and rearwardshifting movements of the load levelling bars during a towing operation.It this slight pivotal movement of the jack assembly and the loadlevelling bar supports assembly was not provided the load levelling barswould shift longitudinally relative to the surfaces upon which they restand possibly produce a snapping or popping sound which might proveirritating to a driver of the vehicle. 7

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art, that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention.

What is claimed is:

l. A trailer hitch comprising draw bar means adapted to be secured to atowing vehicle, first connecting means detachably secured to said drawbar means, second connecting means adapted to be secured to the forwardend of a trailer and detachably engaging said first connecting means,vertical post means mounted on said first connecting means, loadlevelling bar means pivotally mounted on said first connecting means forswinging movement in a generally horizontal plane about said post means,support means adapted to be mounted on said trailer engaging said loadlevelling bar means and cam means disposed intermediate said loadlevelling bar means and said first connecting means for varying theforces transmitted through said load levelling bar means upon swingingmovement of said load levelling bar means about said post means saidload levelling bar means being comprised of two independent housingmembers disposed adjacent to each other and extending rearwardly fromsaid post means, a rearwardly opening socket in each of said sockets, anupstanding bracket having a bore therein orthogonally disposed relativeto said bars secured to the upper surface of each housing memberadjacent each other, and a connecting rod extending between saidbrackets in said bores for pivotally coupling said housing members formovement relative to each other.

2. A trailer hitch as set forth in claim 1 further comprising anti-swaybraking means including a first flat friction member non-rotatablymounted on said first connecting means adjacent said post means and asecond flat friction member operably connected to said load levellingbar means and disposed in engagement with said first friction member forrotation about said vertical post means with said load levelling barmeans whereby force is imparted through said load levelling bar means topress said friction members into engagement with each other.

3. A trailer hitch as set forth in claim 1 wherein said cam means is'comprised of first and second cam discs concentrically disposed aboutsaid post means and having complementary beveled engaging surfaces, oneof said discs being non-rotatably secured to said first connecting meansand the other of said discs having means for connecting said loadlevelling bar means thereto for conjoint rotation.

4. A trailer hitch comprising main body means adapted to be secured to adraw bar means on a towing vehicle, coupling means on said main body forreleasably coupling a trailer to said main body means, post means onsaid main body means disposed in vertical alignment with said couplingmeans, load levelling bar means supported at one end for pivotalmovement about said post means and cam means disposed intermediate saidload levelling bar means and said main body means for varying the forcestransmitted through said load levelling bar means upon pivotal movementof said load levelling bar means relative to said post ifians said loadlli l harl ansb 9 mn i of two independent housing members disposedadjacent to each other and extending rearwardly from said post means, arearwardly opening socket in each of said housing members, a resilientload levelling bar removably disposed in each of said sockets, anupstanding bracket having a bore therein orthogonally disposedrelativeto said bars secured to the upper surface of each housing memberadjacent each other and a connecting rod extending between said bracketsin .said bores for pivotally coupling said housing members for movementrelative to each other.

5. A trailer hitch as set forth in claim 4 further comprising anti-swaybraking means including the first flat friction member non-rotatablymounted on said main body means adjacent said vertical post means and asecond flat friction member rotatably connected to said load levellingbar means and disposed in engagement with said first friction member forrotation about said vertical post means with said load levelling'barmeans whereby the forces imparted to said load levelling bar one of saiddiscs being non-rotatably secured to said main body means and the otherof said discs being opcrably secured to said load levelling bar meansfor conjoint rotation therewith.

1. A trailer hitch comprising draw bar means Adapted to be secured to atowing vehicle, first connecting means detachably secured to said drawbar means, second connecting means adapted to be secured to the forwardend of a trailer and detachably engaging said first connecting means,vertical post means mounted on said first connecting means, loadlevelling bar means pivotally mounted on said first connecting means forswinging movement in a generally horizontal plane about said post means,support means adapted to be mounted on said trailer engaging said loadlevelling bar means and cam means disposed intermediate said loadlevelling bar means and said first connecting means for varying theforces transmitted through said load levelling bar means upon swingingmovement of said load levelling bar means about said post means saidload levelling bar means being comprised of two independent housingmembers disposed adjacent to each other and extending rearwardly fromsaid post means, a rearwardly opening socket in each of said sockets, anupstanding bracket having a bore therein orthogonally disposed relativeto said bars secured to the upper surface of each housing memberadjacent each other, and a connecting rod extending between saidbrackets in said bores for pivotally coupling said housing members formovement relative to each other.
 2. A trailer hitch as set forth inclaim 1 further comprising anti-sway braking means including a firstflat friction member non-rotatably mounted on said first connectingmeans adjacent said post means and a second flat friction memberoperably connected to said load levelling bar means and disposed inengagement with said first friction member for rotation about saidvertical post means with said load levelling bar means whereby force isimparted through said load levelling bar means to press said frictionmembers into engagement with each other.
 3. A trailer hitch as set forthin claim 1 wherein said cam means is comprised of first and second camdiscs concentrically disposed about said post means and havingcomplementary beveled engaging surfaces, one of said discs beingnon-rotatably secured to said first connecting means and the other ofsaid discs having means for connecting said load levelling bar meansthereto for conjoint rotation.
 4. A trailer hitch comprising main bodymeans adapted to be secured to a draw bar means on a towing vehicle,coupling means on said main body for releasably coupling a trailer tosaid main body means, post means on said main body means disposed invertical alignment with said coupling means, load levelling bar meanssupported at one end for pivotal movement about said post means and cammeans disposed intermediate said load levelling bar means and said mainbody means for varying the forces transmitted through said loadlevelling bar means upon pivotal movement of said load levelling barmeans relative to said post means said load levelling bar means beingcomprised to two independent housing members disposed adjacent to eachother and extending rearwardly from said post means, a rearwardlyopening socket in each of said housing members, a resilient loadlevelling bar removably disposed in each of said sockets, an upstandingbracket having a bore therein orthogonally disposed relative to saidbars secured to the upper surface of each housing member adjacent eachother and a connecting rod extending between said brackets in said boresfor pivotally coupling said housing members for movement relative toeach other.
 5. A trailer hitch as set forth in claim 4 furthercomprising anti-sway braking means including the first flat frictionmember non-rotatably mounted on said main body means adjacent saidvertical post means and a second flat friction member rotatablyconnected to said load levelling bar means and disposed in engagementwith said first friction member for rotation about said vertical postmeans with said load levelling bar means whereby the forces imparted tosaid load levelling bar means will press said friction members intoengaGement with each other.
 6. A trailer hitch as set forth in claim 4wherein said cam means is comprised of first and second cam discsconcentrically disposed about said post means and having complementarybeveled engaging surfaces thereon, one of said discs being non-rotatablysecured to said main body means and the other of said discs beingoperably secured to said load levelling bar means for conjoint rotationtherewith.